A magnetic disk device supports a WRITE SAME command. The WRITE SAME command is a command to write a data to a plurality of logical blocks based on particular data. The WRITE SAME command is used at the time of initializing logical blocks in RAID environment, or the like. When the WRITE, SAME command is received, the magnetic disk device executes processings such as receiving particular data received from a host system, generating data of a plurality of logical blocks based on the particular data, and adding encryption or protection information to the generated data of each logical block, and writes each generated data onto the disk. Since the magnetic disk device executes these processings each time the magnetic disk device receives the WRITE SAME command, when the WRITE SAME command is received into the plurality of consecutive logical blocks, it is likely to cause a delay of one rotation waiting for each command.